Page 684 - e-Book

MATERIAL & METHODS

In this study we selected one fresh water lentic water bodies (Jhil area, Mankundu, adjacent
to rail station) to evaluate the phytoplankton diversity & their fluctuation in seasonal pattern.

The samples were taken in between 10 a.m. - 11 a.m. in post monsoon, pre-monsoon and
monsoon season respectively. Here all the samples were taken in 500ml amber colour bottles.

Lugol’s Iodine was used as fixative in 1:100 ratios. The samples were maintained overnight
for suitable sedimentation. The supernatant part was pipette out and the sample being

concentrated to 5ml for analysis. For quantitative estimation of phytoplankton we followed

the “Drop Count Method” (Trivedi & Goel, 1984). Here we used PAST software (V3.19) for
calculation of Species diversity index (Shannon , Shimpson, evenness) & for Rank abundance

analysis. Identifications of the phytoplankton were exercised using standard literature

(Prescott, 1970; Palmer, 1977; Bellinger & Sigee, 2015).
RESULTS & DISCUSSION

In this present study, 22 phytoplankton taxa were recorded from Jhil area of Mankundu.
Among this it has been found that in Jhil area water body Cyanophycean representatives

dominates mostly throughout the season, followed by Chlorophycean & other group (Table
1) .In this case three phytoplankton species build up water bloom . Among this Microcystis

aeruginosa developed bloom almost throughout the season while Nitzschia palea & Euglena

viridis developed bloom in post-monsoon season. All these indicate high organic pollution &
these reflected in the low Species diversity value also (Table 3).

Here we used various diversity indices for their specific quality. Shannon diversity index is
widely used & usually biased towards rare species & the Simpson index indicates its

preference towards dominant species. The rank abundance plots indicate relative species
abundance. Actually this curve indicates both species richness & evenness. Steep gradient

pinto pint low evenness & shallow gradient indicate high evenness.

Variation of the phytoplankton, as a measure of water quality is based on the condition that in
clean water community diversity is high while in the polluted water diversity is low. Wilhm

and Dorris (1966) have proposed a relationship between Shannon diversity and pollution

status of the sampling sites and defined the zones as follows (Table 4) & indicate moderate
pollution ststus.

This lentic water body is associated with various human activities, like fishing, washing of
garments, cattle washing etc. The Jhil area waterbody also connected with the drainage

system of surrounding areas. This gradually increases the organic load. This leads to
reduction in the self purification property of the water & the modified status only support few

674